Moviegoers know that many special effects are created by compute

Moviegoers know that many special effects are created by computers．they often don′t know is that these scenes still require a lot of work．
A、That
B、Whom
C、What
D、How
【正确答案】：C
【题目解析】：【考情点拨】考查主语从句引导词。 【应试指导】句意：常看电影的人知道许多特效都是通过电脑制作出来的。但他们往往不知道的是制作这些场景还需要投入大量的工作。分析句子结构可知．空格所在从句在整个句子中充当主语，从句中缺少宾语，且宾语指的是事而非人，故选C。